but the sandy desert is also a good place to grow princess potatoes. and they can be harvested at a time of the year when there aren't any new potatoes in germany. there is one drawback, however -- the fields need to be irrigated, and water is a very valuable resource in egypt. >> the soil has to be damp and wet. so that's what we do. we water the soil, we rrigate the soil, and then we start to. >> meter by meter, the water is turning the sand into fertile soil. the ground water comes from a well 150 meters deep. this is not exactly environmentally sustainable agriculture. meanwhile, back in germany, the discount supermarkets won't stock christoph schÄfer's organic potatoes in the spring because they prefer the potatoes from egypt. >> when we have a dry summer, we only need to irrigate two times to get a good potato harvest. in egypt and other countries, where water is in very short supply, they need to irrigate much more often. >> about 96% of egypt is covered by desert, so irrigation is the only way to carry out large- scale farming. and for egyptia